Eutrophication is a persistent threat to aquatic ecosystems worldwide. Foundation species, namely those that play a central role in the structuring of communities and functioning of ecosystems, are likely important for the resilience of aquatic ecosystems in the face of disturbance. However, little is known about how interactions among such species influence ecosystem responses to nutrient perturbation. Here, using an array (N = 20) of outdoor experimental pond ecosystems (15,000 L), we manipulated the presence of two foundation species, the macrophyte Myriophyllum spicatum and the mussel Dreissena polymorpha, and quantified ecosystem responses to multiple nutrient disturbances, spread over two years. In the first year, we added five nutrient pulses, ramping up from 10 to 50 μg P/L over a 10-week period from mid-July to mid-October, and in the second year, we added a single large pulse of 50 μg P/L in mid-October. We used automated sondes to measure multiple ecosystems properties at high frequency (15-minute intervals), including phytoplankton and dissolved organic matter fluorescence, and to model whole-ecosystem metabolism. Overall, both foundation species strongly affected the ecosystem responses to nutrient perturbation, and, as expected, initially suppressed the increase in phytoplankton abundance following nutrient additions. However, when both species were present, phytoplankton biomass increased substantially relative to other treatment combinations: non-additivity was evident for multiple ecosystem metrics following the nutrient perturbations in both years but was diminished in the intervening months between our perturbations. Overall, these results demonstrate how interactions between foundation species can cause surprisingly strong deviations from the expected responses of aquatic ecosystems to perturbations such as nutrient additions.

中文翻译：

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基础物种的非加性效应决定了水生生态系统对养分扰动的响应

富营养化是对全世界水生生态系统的持续威胁。基础物种，即那些在群落结构和生态系统功能中发挥核心作用的物种，可能对水生生态系统在受到干扰时的恢复能力很重要。然而，关于这些物种之间的相互作用如何影响生态系统对养分扰动的反应知之甚少。在这里，使用 室外实验池塘生态系统（15,000 L）的阵列（N = 20），我们操纵了两种基础物种的存在，大型植物Myriophyllum spicatum和贻贝Dreissena polymorpha，并量化生态系统对多种营养物质干扰的反应，传播时间超过两年。在第一年，我们添加了五个营养脉冲，从 7 月中旬到 10 月中旬的 10 周内从 10 μg P/L 增加到 50 μg P/L，在第二年，我们添加了 50 μg 的单个大脉冲10 月中旬的微克 P/L。我们使用自动探测器以高频（15 分钟间隔）测量多个生态系统特性，包括浮游植物和溶解有机物荧光，并模拟整个生态系统的新陈代谢。总体而言，这两种基础物种都强烈影响了生态系统对养分扰动的反应，并且正如预期的那样，最初抑制了添加养分后浮游植物丰度的增加。然而，当这两个物种都存在时，相对于其他处理组合，浮游植物生物量显着增加：在这两年营养物扰动之后，多个生态系统指标的非可加性是明显的，但在我们扰动之间的间隔月份中减少了。总体而言，这些结果表明，基础物种之间的相互作用如何导致水生生态系统对营养添加等扰动的预期响应出现惊人的强烈偏差。